Types And Classification Of Solids
Category : JEE Main & Advanced
(1) Types of solids
Solids can be broadly classified into following two types,
(i) Crystalline solids/True solids,
(ii) Amorphous solids/Pseudo solids
|
Crystalline solids |
Amorphous solids |
|
They have long range order. |
They have short range order. |
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They have definite melting point |
Not have definite melting point |
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They have a definite heat of fusion |
Not have definite heat of fusion |
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They are rigid and incompressible |
Not be compressed to any appreciable extent |
|
They are given cleavage i.e. they break into two pieces with plane surfaces |
They are given irregular cleavage i.e. they break into two pieces with irregular surface |
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They are anisotropic because of these substances show different property in different direction |
They are isotropic because of these substances show same property in all directions |
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There is a sudden change in volume when it melts. |
There is no sudden change in volume on melting. |
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These possess symmetry |
Not possess any symmetry. |
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These possess interfacial angles. |
Not possess interfacial angles. |
(2) Crystalline and amorphous silica \[(Si{{O}_{2}})\]
Silica occurs in crystalline as well as amorphous states. Quartz is a typical example of crystalline silica. Quartz and the amorphous silica differ considerably in their properties.
|
Quartz |
Amorphous silica |
|
It is crystalline in nature |
It is light (fluffy) white powder |
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All four corners of \[SiO_{4}^{4-}\] tetrahedron are shared by others to give a network solid |
The \[SiO_{4}^{4-}\] tetrahedra are randomly joined, giving rise to polymeric chains, sheets or three-dimensional units |
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It has high and sharp melting point (1710°C) |
It does not have sharp melting point |
(3) Diamond and graphite
Diamond and graphite are tow allotropes of carbon. Diamond and graphite both are covalent crystals. But, they differ considerably in their properties.
|
Diamond |
Graphite |
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It occurs naturally in free state |
It occurs naturally, as well as manufactured artificially |
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It is the hardest natural substance known. |
It is soft and greasy to touch |
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It has high relative density (about 3.5) |
Its relative density is 2.3 |
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It is transparent and has high refractive index (2.45) |
It has black in colour and opaque |
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It is non-conductor of heat and electricity. |
Graphite is a good conductor of heat and electricity |
|
It burns in air at 900°C to give CO2 |
It burns in air at 700°C to give CO2 |
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It occurs as octahedral crystals |
It occurs as hexagonal crystals |
(4) Classification of crystalline solids
Some characteristics of different types of crystalline solids
|
Types of Solid |
Constituents |
Bonding |
Examples |
Physical Nature |
M.P. |
B.P. |
Electrical Conductivity |
|
Ionic |
Positive and negative ions network systematically arranged |
Coulombic
|
NaCl, KCl, CaO, MgO, LiF, ZnS, BaSO4 and K2SO4 etc. |
Hard but brittle |
High (?1000K) |
High (?2000K) |
Conductor (in molten state and in aqueous solution) |
|
Covalent |
Atoms connected in covalent bonds |
Electron sharing
|
SiO2 (Quartz), SiC, C (diamond), C(graphite) etc. |
Hard Hard Hard |
Very high (?4000K) |
Very high (?5000K) |
Insulator except graphite |
|
Molecular |
Polar or non-polar molecules |
(i) Molecular interactions (intermolecu-lar forces) (ii) Hydrogen bonding
|
I2,S8, P4, CO2, CH4, CCl4 etc.
Starch, sucrose, water, dry ice or drycold (solid CO2) etc. |
Soft
Soft |
Low (?300K to 600K)
Low (?400K) |
Low (? 450 to 800 K)
Low (?373K to 500K) |
Insulator
Insulator |
|
Metallic |
Cations in a sea of electrons
|
Metallic
|
Sodium , Au, Cu, magnesium, metals and alloys |
Ductile malleable |
High (?800K to 1000 K) |
High (?1500K to 2000K) |
Conductor |
|
Atomic |
Atoms |
London dispersion force |
Noble gases |
Soft |
Very low |
Very low |
Poor thermal and electrical conductors |
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